Far-optical device

ABSTRACT

A far-optical device comprising a reversal system and an adjustable optical magnification means with more than fourfold magnification, wherein the far-optical device has an optical beam deflection means which at all magnifications ensures a subjective field of view of the far-optical device of at least 22° at least for light of a wavelength of about 550 nm.

This application is a continuation of U.S. application Ser. No.14/305,849, filed Jun. 16, 2014, which is a continuation of U.S.application Ser. No. 13,234,705, filed Sep. 16, 2011, issued as U.S.Pat. No. 8,786,947, which is a continuation of U.S. application Ser. No.12,793,073, filed Jun. 3, 2010, issued as U.S. Pat. No. 8,054,544, whichis a continuation of U.S. application Ser. No. 11/453,983, filed Jun.16, 2006, issued as U.S. Pat. No. 7,742,228, which claims priority fromAustrian Patent Application No. A1220/2005 filed Jul. 20, 2005, thedisclosures of which are incorporated herein by reference.

The present invention relates to a far-optical device, in particular atelescope or aiming telescope, comprising a reversal system and anadjustable optical magnification means with more than fourfoldmagnification.

If an object at a great distance is viewed with the naked eye it appearsat a small angle. The purpose of any far-optical device is to magnifythat small angle. The far-optical device thereform provides that anappearance angle which is as large as possible can pass into the eye ofthe viewer. At the same time it should be possible to overlook a pieceof territory which is as large as possible.

In the case of zoomable far-optical devices of the general kind setforth, involving an adjustable magnification, it is particularlycritical to be able to overlook a piece of territory which is as largeas possible, over the entire magnification range.

The object of the invention is to improve far-optical devices of thegeneral kind set forth, in that respect.

In accordance with the invention that is achieved in that thefar-optical device has an optical beam deflection means which at allmagnifications ensures a subjective field of view of the far-opticaldevice of at least 22°, preferably between 22° and 24°, at least forlight of a wavelength of about 550 nm.

By means of the optical beam deflection means, it is now possible toafford a subjective field of view of at least 22°, even at low levels ofmagnification, in particular at the lowest magnification, of thefar-optical device. That was possible hitherto only at relatively highlevels of magnification of far-optical devices of the general kind setforth. Accordingly, even at low levels of magnification, by means of thefar-optical device according to the invention, the viewing person sees alarger piece of territory than the state of the art hitherto permitted.

In accordance with a further aspect of the invention the specifiedobject is also attained if it is provided that the beam deflection meansat the maximum magnification ensures a total focal length of thereversal system of between 11 mm and 7 mm, preferably between 10 mm and8 mm.

Further details and features of the invention are explained withreference to the Figures described hereinafter, in which:

FIG. 1 shows a longitudinal section through an aiming telescope inaccordance with the state of the art,

FIGS. 2a to 2c each show a section through a reversal system inaccordance with the state of the art,

FIGS. 3a to 3c each show a section through a reversal system for anembodiment according to the invention of an aiming telescope, and

FIG. 4 shows a diagrammatic measurement structure for determining thesubjective field of view.

FIG. 1 diagrammatically shows a section through an aiming telescope ortelescopic sight in accordance with the state of the art. On the sidetowards the object when viewing, the telescope has a lens arrangementwhich is referred to hereinafter as the objective 4 while on the sidetowards the eye of the viewer it has a lens system identified as theeyepiece 5. Disposed between the objective 4 and the eyepiece 5 is thecentral tube 6. It frequently carries one or more adjusting towers 8with which various adjustment functions known in the state of the artcan be carried out. Disposed within the central tube between theobjective 4 and the eyepiece 5 is the reversal system 1. That is anoptical system which is known in the state of the art and which servesto make the image produced by the objective 4 upright. The reversalsystem 1 is generally arranged between the objective-side image plane 9and the eyepiece-side image plane 10. In addition the reversal system 1frequently serves not only for making the image upright but also formagnifying the intermediate image produced in the objective-side imageplane 9. In the aiming telescope shown in FIG. 1 the opticalmagnification means is integrated into the reversal system 1. Theoptical magnification means and the reversal system are thus provided inone component.

Two optical elements 3 a and 3 b are provided for magnifying the imageand making it upright. In general these involve achromatic elementswhich for controlling chromatic aberration are desirably in the form ofwhat are referred to as cemented lenses, that is to say lensarrangements which are bonded together. In the state of the art as alsoin the case of reversal systems or far-optical devices in accordancewith the invention they appropriately have refractive powers of +20 dpt(dioptres) up to +53 dpt, preferably from +21 dpt to +35 dpt,particularly preferably in the range between +23 dpt and +26 dpt. Inorder to make the magnification of the illustrated aiming telescopeadjustable, the optical elements 3 a and 3 b are movable along controlgrooves. Displacement of the optical elements 3 a and 3 b means that theintermediate image produced by the objective 4 in the objective-sideimage plane 9 is produced, with the changing imaging scale and in anupright position, in the eyepiece-side image plane 10. In theillustrated embodiment the spacing of the two image planes 9 and 10 isnot changed by the displacement of the optical elements 3 a and 3 b. Inthe state of the art moreover it was also known additionally also toprovide a field lens 11. That helps to pass the beam of rays, comingfrom the objective 4, of an object point at the edge of the field ofview, through the narrow passage of the central tube 6 and the reversalsystem 1 respectively.

The change in the imaging scale by movement of the optical elements 3 aand 3 b along control grooves (not further shown in detail here) isknown in the state of the art. FIGS. 2a to 2c show the positions of theoptical elements 3 a and 3 b at different levels of magnification. Theposition shown in FIG. 2a provides for example single magnification. Inthe position shown in FIG. 2b the reversal system 1 produces amagnification by 2.5 times while in the position shown in FIG. 2c itproduces magnification by 4 times.

In order now to be able to ensure a subjective field of view of at least22° in a far-optical device with a maximum magnification or a maximumzoom of greater than four times, even at low levels of magnification,the invention provides an optical beam deflection means 2. That is shownin an embodiment in FIGS. 3a to 3c and is here integrated in the form ofan additional lens arrangement in the reversal system 1. The reversalsystem 1 according to the invention as shown in FIGS. 3a to 3c can beintegrated for example in place of the reversal system 1 shown therein,in an aiming telescope as shown in FIG. 1.

The optical beam deflection means 2 however can equally well be arrangedin the form of a separate component, separately from the reversal system1, in the far-optical device. On the other hand however it is alsopossible for the optical beam deflection means 2 according to theinvention to be embodied by a suitable configuration of the lenses 11, 3a and 3 b. It is desirably provided that the optical beam deflectionmeans ensures the subjective field of view of at least 22°, preferablybetween 22° and 24°, in relation to an optical magnification means,preferably of the reversal system, with an at least fivefold andpreferably at an at least sixfold, maximum magnification, at allmagnification stages. For better control of chromatic aberration it hasbeen found to be appropriate for the optical beam deflection means 2 tohave preferably two lenses 7 which are bonded together, that is to saycemented lenses. It would however also be conceivable for the opticalbeam deflection means 2 to be in the form of an individual lens.

It has proven to be desirable for the optical beam deflection means 2 tobe arranged on the side of the reversal system 1, which faces towardsthe eyepiece 5. In that respect positioning on the side of theeyepiece-side image plane 10, which faces away from the eyepiece 5, isadvantageous.

A solution which is structurally particularly simple provides that theoptical beam deflection means 2 is arranged fixedly, that is to say notmovably with respect to the central tube 6. In certain embodimentshowever it has also proven to be necessary for the optical beamdeflection means 2 to be designed to be movable, that is to saygenerally displaceable along the optical axis.

Hitherto, in current aiming telescopes, the central tube is of anoutside diameter of between 30 mm and 35 mm. That is naturally reckonedwithout any adjusting towers 8 or the like which may be present. Thatdimension for the central tube 6 is desirably also retained in the caseof aiming telescopes according to the invention.

In general it is desirable for the optical beam deflection means 2 tohave a refractive power of between −20 dpt (dioptres) and −40 dpt,preferably between −27 dpt and −37 dpt. In a specific example, therefractive power provided is −27.03 dpt, in which case a subjectivefield of view of 23.5° is achieved at all levels of magnification.

FIGS. 3a to 3c again show the reversal system 1 according to theinvention in three different positions of the optical elements 3 a and 3b provided for magnification and reversal of the image. The position inFIG. 3a involves for example single magnification. FIG. 3b shows thepositioning with a magnification of 3.5 times and FIG. 3c showspositioning at a magnification of six times. The optical beam deflectionmeans 2 provides for an increase in the size of the subjective field ofview by beam deflection. In that way, in accordance with the invention,at all levels of magnification it is possible to achieve a subjectivefield of view of at least 22° or at the maximum magnification a totalfocal length of smaller than or equal to 11 mm. By virtue of the beamdeflection means 2, at the maximum magnification, the total focal lengthof the reversal system 1 according to the invention is desirably between11 mm and 7 mm, preferably between 10 mm and 8 mm. In the specificembodiment mentioned a total focal length of 8.264 mm was achieved, atthe maximum magnification.

The size of the subjective field of view 2 ω′ is determined by means ofangle measurement. The corresponding measurement structure fortestpieces with a real exit pupil is shown in FIG. 4. On the eyepieceside of the testpiece 25 an auxiliary telescope 28 is mounted on aturntable with an angle measurement device. In that respect an auxiliarytelescope 28 with approximately threefold magnification, a diameter forthe entry pupil of about 3 mm and an arrow mark such as for example acrosshairs was to be used. To avoid colour fringes in the image greenlight of a wavelength of about 550 nm is used for the measurementprocedure. The measurement structure provides a sequence comprising alight source 21, a condenser 22, a filter 23, a diffusing screen 24, afar-optical device (testpiece) 25 to be tested, a field of view stop 26and an auxiliary telescope 28 on the position 27 of the exit pupil. Tocarry out the measurement procedure the pivot axis of the auxiliarytelescope 28 is at the location of the exit pupil 27 and in the plane ofthe entry pupil of the auxiliary telescope. The pivot axis intersectsthe optical axis of the testpiece 25 and that of the auxiliary telescope28 at a right angle. The auxiliary telescope 28 which is set at an acuteangle in relation to the field of view stop 26 of the testpiece 25 is tobe pivoted in order to move the arrow mark thereof successively tomutually opposite edges of the field of view. The angular difference isto be read off at the scale of the angle measurement device of thepivotal table (in degrees).

Measurement of the total focal length of a reversal system is effectedin accordance with DIN 58189 (issued in May 1996) and can be carried outwith commercially available testing apparatuses.

The invention claimed is:
 1. An aiming telescope comprising: an objective lens and an eyepiece lens; a central tube disposed between the objective lens and the eyepiece lens, wherein the central tube comprises a narrow passage having a maximum outside diameter between 35 mm and 30 mm; a reversal system, wherein the reversal system is arranged in the narrow passage of the central tube and between an objective-side image plane and an eyepiece-side image plane, wherein the reversal system is for magnifying an intermediate image produced in the objective-side image plane, wherein the reversal system has two optical elements with positive refractive powers, wherein said two optical elements are movable relative to each other, so that said intermediate image produced by the objective lens in the objective-side image plane is produced, with a changeable imaging scale and in an upright position, in the eyepiece-side image plane; and an optical beam deflection means disposed on a side of the reversal system facing the eyepiece lens, wherein the optical beam deflection means is arranged on a side of an eye-piece side image plane which faces away from the eyepiece lens, such that at a maximum magnification of the aiming telescope a total focal length for the reversal system is at most 11 mm.
 2. The aiming telescope according to claim 1, wherein the optical beam deflection means at the maximum magnification ensures a total focal length for the reversal system of between 11 mm and 7 mm.
 3. The aiming telescope according to claim 2, wherein the optical beam deflection means at the maximum magnification ensures a total focal length for the reversal system of between 10 mm and 8 mm.
 4. The aiming telescope according to claim 1, wherein a maximum value of the changeable imaging scale is greater than four times.
 5. The aiming telescope according to claim 4, wherein the maximum value of the imaging scale is at least fivefold.
 6. The aiming telescope according to claim 5, wherein the maximum value of the changeable imaging scale is least sixfold.
 7. The aiming telescope according to claim 1, wherein at all magnifications of the aiming telescope a subjective field of view of the aiming telescope is at least 22°.
 8. The far aiming telescope according to claim 1, wherein the optical beam deflection means has a refractive power of between −20 dpt and −40 dpt.
 9. The aiming telescope according to claim 8, wherein the optical beam deflection means has a refractive power of between −27 dpt and −37 dpt. 